Fiber reinforced thermoplastic sheets with surface coverings

ABSTRACT

A composite sheet material that includes at least one porous core layer including a thermoplastic material and from about 20 weight percent to about 80 weight percent fibers based on a total weight of the porous core layer, and at least one skin covering a surface of the core layer. The skin includes at least one of a thermoplastic film, a fiber based scrim, a non-woven fabric, and a woven fabric.

BACKGROUND OF THE INVENTION

This invention relates generally to porous fiber-reinforcedthermoplastic polymer composite sheets, and more particularly to porousfiber-reinforced thermoplastic polymer composite sheets having surfacecoverings providing for at least one of reduced flame spread, reducedsmoke density, reduced heat release, and reduced gas emissions.

Porous fiber-reinforced thermoplastic composite sheets have beendescribed in U.S. Pat. Nos. 4,978,489 and 4,670,331 and are used innumerous and varied applications in the product manufacturing industrybecause of the ease molding the fiber reinforced thermoplastic sheetsinto articles. For example, known techniques such as thermo-stamping,compression molding, and thermoforming have been used to successfullyform articles from fiber reinforced thermoplastic sheets.

Because of the varied applications, fiber-reinforced thermoplasticsheets are subjected to various performance tests. For example flamespread, smoke density, and gaseous emissions characteristics of thefiber-reinforced thermoplastic sheets are important when the formedarticles are used in environments that might be subjected to a flameevent, such as a fire. Because of safety concerns, there is a need toimprove the flame, smoke and toxicity performance of fiber reinforcedthermoplastic sheet products.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a composite sheet material is provided that includes atleast one porous core layer including at least one thermoplasticmaterial and from about 20 weight percent to about 80 weight percentfibers based on a total weight of said porous core layer, and at leastone skin. Each skin covering at least a portion of a surface of the atleast one porous core layer. The skin includes at least one of athermoplastic film, an elastomeric film, a metal foil, a thermosettingcoating, an inorganic coating, a fiber based scrim, a non-woven fabric,and a woven fabric, said skin having a limiting oxygen index greaterthan about 22, as measured per ISO 4589.

In another aspect, a method of manufacturing a porous fiber-reinforcedthermoplastic sheet is provided. The method includes providing a porousfiber-reinforced thermoplastic sheet having at least one porous corelayer including a thermoplastic material and from about 20 weightpercent to about 80 weight percent fibers. The method also includeslaminating at least one skin to a surface of the porous fiber-reinforcedthermoplastic sheet. Each skin includes at least one of a thermoplasticfilm, an elastomeric film, a metal foil, a thermosetting coating, aninorganic coating, a fiber based scrim, a non-woven fabric, and a wovenfabric, the skin having a limiting oxygen index greater than about 22,as measured per ISO 4589, to enhance at least one of the flame, smoke,heat release and gaseous emissions characteristics of the porousfiber-reinforced thermoplastic sheet.

In another aspect, a composite sheet material is provided that includesa permeable core including discontinuous fibers bonded together with athermoplastic resin. The permeable core having a density from about 0.2gm/cc to about 1.8 gm/cc, and including a surface region. The compositesheet material also includes an adherent layer adjacent to the surfaceregion. The adherent layer including a material having a limiting oxygenindex greater than about 22, as measured in accordance with ISO 4589.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is cross sectional illustration of an exemplary fiber reinforcedthermoplastic sheet in accordance with an embodiment of the presentinvention.

FIG. 2 is cross sectional illustration of an exemplary fiber reinforcedthermoplastic sheet in accordance with another embodiment of the presentinvention.

FIG. 3 is cross sectional illustration of an exemplary fiber reinforcedthermoplastic sheet in accordance with another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Multi-layered porous fiber-reinforced thermoplastic composite sheetshaving characteristics of reduced flame spread, reduced smoke density,reduced heat release, and reduced gas emissions are described below indetail. In an exemplary embodiment, the multi-layered porousfiber-reinforced thermoplastic sheets include one or more porous corelayers that are formed from one or more thermoplastic materials andabout 20 weight percent to about 80 weight percent of fibers dispersedin the thermoplastic material. At least one surface of the core layer iscovered by a skin laminated to the core layer under heat and/or pressurewith or without the use of an adhesive or a tie layer. The skinmaterials are chosen, at least in part, to impart the desired reductionin flame spread, heat release, smoke density, and gaseous emissions ofthe composite sheet when exposed to a fire event. Also, handling,moldability and end use performance can be improved by laminating two ormore porous core layers together having different thermoplasticmaterials and/or different fibers. Further, skins can be laminatedbetween core layers to affect performance characteristics. Additionally,moldability and formability can be improved by laminating at least oneskin to a surface of the core layer where the skin is at least one of afiber-based scrim, a non-woven fabric and a woven fabric.

Referring to the drawings, FIG. 1 is a cross sectional illustration ofan exemplary fiber reinforced thermoplastic composite sheet 10 thatincludes one porous core layer 12 and skins 14 and 16 laminated to outersurfaces 18 and 20 of core layer 12. In one embodiment, composite sheet10 has a thickness of about 0.5 mm to about 50 mm and in anotherembodiment, a thickness of about 0.5 mm to about 25 mm. Also, skins 14and 16 each have a thickness in one embodiment of about 25 micrometersto about 5 mm, and in another embodiment from about 25 micrometers toabout 2.5 mm.

Core layer 12 is formed from a web made up of open cell structuresformed by random crossing over of reinforcing fibers held together, atleast in part, by one or more thermoplastic resins, where the voidcontent of porous core layer 12 ranges in general between about 5% andabout 95% and in particular between about 30% and about 80% of the totalvolume of core layer 12. In an another embodiment, porous core layer 12is made up of open cell structures formed by random crossing over ofreinforcing fibers held together, at least in part, by one or morethermoplastic resins, where about 40% to about 100% of the cellstructure are open and allow the flow of air and gases through. Corelayer 12 has a density in one embodiment of about 0.2 gm/cc to about 1.8gm/cc and in another embodiment about 0.3 gm/cc to about 1.0 gm/cc. Corelayer 12 is formed using known manufacturing process, for example, a wetlaid process, an air laid process, a dry blend process, a carding andneedle process, and other known process that are employed for makingnon-woven products. Combinations of such manufacturing processes arealso useful. Core layer 12 includes about 20% to about 80% by weightfibers having a high tensile modulus of elasticity and an average lengthof between about 7 and about 200 mm, and about 20% to about 80% byweight of a wholly or substantially unconsolidated fibrous orparticulate thermoplastic materials, where the weight percentages arebased on the total weight of core layer 12 In another embodiment, corelayer includes about 35% to about 55% by weight fibers. The web isheated above the glass transition temperature of the thermoplasticresins on core layer 12 to substantially soften the plastic materialsand is passed through one or more consolidation devices, for example niprollers, calendaring rolls, double belt laminators, indexing presses,multiple daylight presses, autoclaves, and other such devices used forlamination and consolidation of sheets and fabrics so that the plasticmaterial can flow and wet out the fibers. The gap between theconsolidating elements in the consolidation devices are set to adimension less than that of the unconsolidated web and greater than thatof the web if it were to be fully consolidated, thus allowing the web toexpand and remain substantially permeable after passing through therollers. In one embodiment, the gap is set to a dimension about 5% toabout 10% greater than that of the web if it were to be fullyconsolidated. A fully consolidated web means a web that is fullycompressed and substantially void free. A fully consolidated web wouldhave less than 5% void content and have negligible open cell structure.

A high tensile modulus of elasticity means a tensile modulus ofelasticity substantially higher than that of a consolidated sheet whichcould be formed from the web structure. Fibers falling into thiscategory include metal, metalized inorganic, metalized synthetic, glass,graphite, carbon and ceramic fibers and fibers such as the aramid fiberssold under the trade names Kevlar and Nomex, and generally includes anyfiber having a tensile modulus higher than about 10,000 Mega Pascals atroom temperature and pressure.

Particulate plastic materials include short plastics fibers which can beincluded to enhance the cohesion of the web structure duringmanufacture. Bonding is effected by utilizing the thermalcharacteristics of the plastic materials within the web structure. Theweb structure is heated sufficiently to cause the thermoplasticcomponent to fuse at its surfaces to adjacent particles and fibers.

In one embodiment, individual reinforcing fibers should not on heaverage be shorter than about 7 millimeters, because shorter fibers donot generally provide adequate reinforcement in the ultimate moldedarticle. Also, fibers should not on average be longer than about 200millimeters since such fibers are difficult to handle in themanufacturing process.

In one embodiment, glass fibers are used, and in order to conferstructural strength the fibers have an average diameter between about 7and about 22 microns. Fibers of diameter less than about 7 microns caneasily become airborne and can cause environmental health and safetyissues. Fibers of diameter greater than about 22 microns are difficultto handle in manufacturing processes and do not efficiently reinforcethe plastics matrix after molding.

In one embodiment, the thermoplastics material is, at least in part, ina particulate form. Suitable thermoplastics include, but are not limitedto, polyethylene, polypropylene, polystyrene, acrylonitrylstyrene,butadiene, polyethyleneterephthalate, polybutyleneterephthalate,polybutyleneterachlorate, and polyvinyl chloride, both plasticised andunplasticised, and blends of these materials with each other or otherpolymeric materials. Other suitable thermoplastics include, but are notlimited to, polyarylene ethers, polycarbonates, polyestercarbonates,thermoplastic polyesters, polyetherimides,acrylonitrile-butylacrylate-styrene polymers, amorphous nylon,polyarylene ether ketone, polyphenylene sulfide, polyaryl sulfone,polyether sulfone, liquid crystalline polymers, poly(1,4 phenylene)compounds commercially known as PARMAX®, high heat polycarbonate such asBayer's APEC® PC, high temperature nylon, and silicones, as well asalloys and blends of these materials with each other or other polymericmaterials. Preferably, the thermoplastic material has a limited oxygenindex (LOI) greater than about 22, as measured in accordance with ISO4589 test method. It is anticipated that any thermoplastics resin can beused which is not chemically attacked by water and which can besufficiently softened by heat to permit fusing and/or molding withoutbeing chemically or thermally decomposed.

In one embodiment, the plastic particles need not be excessively fine,but particles coarser than about 1.5 millimeters are unsatisfactory inthat they do not flow sufficiently during the molding process to producea homogenous structure. The use of larger particles can result in areduction in the flexural modulus of the material when consolidated. Inone embodiment, the plastics particles are not more than about 1millimeter in size.

Referring to FIG. 1, skins 14 and 16 are formed from materials that canwithstand processing temperatures of between about 200° C. and about425° C. Skins 14 and 16 can be thermoplastic films, elastomeric films,metal foils, thermosetting coating, inorganic coatings, fiber reinforcedscrims, and woven or non-woven fabric materials. Any suitablethermoplastic material, including blends of thermoplastic materials,having a LOI greater than about 22, as measured in accordance with ISO4589 test method, can be used for forming the thermoplastic films, forexample, poly(ether imide), poly(ether ketone), poly(ether-etherketone), poly(phenylene sulfide), poly(ether sulfone),poly(amide-imide), poly(aryl sulfone) and combinations thereof. Suitablefibers for forming the scrims include, but are not limited to, glassfibers, aramid fibers, carbon fibers, inorganic fibers, metal fibers,metalized synthetic fibers, metalized inorganic fibers, and combinationsthereof. Preferably, the fibers used in forming the scrims have a LOIgreater than about 22, as measured in accordance with ISO 4589 testmethod.

In one embodiment, the inorganic coating includes a layer of at leastone of gypsum paste, a calcium carbonate paste, a mortar and a concrete.The fiber-based scrim includes a lightweight non-woven covering materialmanufactured via wet laid, air laid, spunbond, and spunlace processes.The fiber based scrim includes, for example, glass, carbon,polyacrylonitrile, aramid, poly(p-phenylene-benzobisoxazole),poly(ether-imide), poly(phenylene sulfide), etc. The non-woven fabricincludes a thermoplastic material, a thermal setting binder, inorganicfibers, metal fibers, metallized inorganic fibers and metallizedsynthetic fibers.

Skins 14 and 16 are laminated to core layer 12 by any suitablelamination process using heat and/or pressure with or without the use ofan adhesive or a tie layer, for example using nip rollers or alamination machine. Skins 14 and 16 are laminated to core 12 after ithas been formed, and in one embodiment, skins 14 and 16 are laminated tocore layer 12 before it has been cut into sheets of predetermined size.In another embodiment, skins 14 and 16 are laminated to core layer 12after it has been cut into sheets. In one embodiment, the temperature ofthe lamination process is greater than the glass transition temperatureof the thermoplastic resins of the skins and core layer, for example,greater than about 100° C. In another embodiment, skins 14 and 16 arebonded to core layer 12 at room temperature using thermal settingadhesives and pressure.

FIG. 2 is a cross sectional illustration of another exemplary fiberreinforced thermoplastic sheet 30 that includes core layers 32 and 34,and skins 36, 38 and 40 laminated to core layers 32 and 34.Particularly, core layer 32 includes a first surface 42 and a secondsurface 44, and core layer 34 includes a first surface 46 and a secondsurface 48. Core layers 32 and 34 are arranged so that second surface 44of core layer 32 is adjacent to first surface 46 of core layer 34. Skin36 is positioned over first surface 42 of core layer 32, skin 38 ispositioned over second surface 48 of core layer 34, and skin 40 ispositioned between second surface 44 of core layer 32 and first surface46 of core layer 34. Core layers 32 and 34, and skins 36, 38, and 40 arelaminated together to form fiber reinforced thermoplastic sheet 30.

Core layers 32 and 34, similar to core layer 12 described above,includes about 20% to about 80% by weight fibers having a high tensilemodulus of elasticity and about 20% to about 80% by weight ofthermoplastics material. The thermoplastic material and/or the fibers ofcore layer 32 can be the same or different from the thermoplasticmaterial and/or the fibers of core layer 34 depending on the desiredproperties of sheet 30.

Skins 36, 38, and 40, similar to skins 14 and 16 described above, areformed from materials that can withstand processing temperatures ofbetween about 200° C. and about 425° C. Skins 36, 38, and 40 can bethermoplastic films, fiber reinforced scrims, and woven or non-wovenfabric materials. Skins 36, 38, and 40 can be formed from the samematerials or can be formed from different materials depending on thedesired properties of sheet 30.

In an alternate embodiment, sheet 30 does not include skin 40 laminatedbetween core layers 32 and 34. In further alternate embodiments, onlyone of the outer surfaces of sheet 30 includes a skin and/or a skinlaminated between core layers 32 and 34. In a further alternateembodiment, sheet 30 includes a skin or a skin 40 laminated between corelayers 32 and 34 that covers at least a part of second surface 44 ofcore layer 32 and first surface 46 of core layer 34.

FIG. 3 is a cross sectional illustration of another exemplary fiberreinforced thermoplastic sheet 60 that includes porous core layers 62,64, and 66, and skins 68, 70, 72, and 74 laminated to core layers 62,64, and 66. Particularly, core layer 62 includes a first surface 76 anda second surface 78, core layer 64 includes a first surface 80 and asecond surface 82, and core layer 66 includes a first surface 84 and asecond surface 86. Core layers 62, 64, and 66 are arranged so thatsecond surface 78 of core layer 62 is adjacent to first surface 80 ofcore layer 64, and second surface 82 of core layer 64 is adjacent tofirst surface 84 of core layer 66. Skin 68 is positioned over firstsurface 76 of core layer 62, skin 70 is positioned over second surface86 of core layer 66, skin 72 is positioned between second surface 78 ofcore layer 62 and first surface 80 of core layer 64, and skin 74 ispositioned between second surface 82 of core layer 64 and first surface84 of core layer 66. Core layers 62, 64, and 66, and skins 68, 70, 72,and 74 are laminated together to form fiber reinforced thermoplasticsheet 60.

Core layers 62, 64, and 66, similar to core layer 12 described above,includes about 20% to about 80% by weight fibers having a high modulusof elasticity and about 20% to about 80% by weight of one or morethermoplastic materials. The thermoplastic material and/or the fibers ofeach core layer 62, 64, and 66 can be the same or different from thethermoplastic material and/or the fibers of each other core layerdepending on the desired properties of sheet 60.

Skins 68, 70, 72, and 74, similar to skins 14 and 16 described above,are formed from materials that can withstand processing temperatures ofbetween about 200° C. and about 425° C. Skins 68, 70, 72, and 74 can bethermoplastic films, fiber reinforced scrims, and woven or non-wovenfabric materials. Skins 68, 70, 72, and 74 can be formed from the samematerials or can be formed from different materials depending on thedesired properties of sheet 60. In an alternate embodiments, sheet 60includes one or more of skins 68, 70, 72, and 74 but not all four skins.In another embodiment, sheet 60 includes one or more of skins 68, 70,72, and 74 covering at least a part of the surfaces of core layers 62,64, and 66.

The porous fiber-reinforced thermoplastic composite sheets describedabove can be used in, but not limited to, building infrastructure,aircraft, train and naval vessel side wall panels, ceiling panels, cargoliners, office partitions, elevator shaft lining, ceiling tiles,recessed housing for light fixtures and other such applications that arecurrently made with honeycomb sandwich structures, thermoplastic sheets,and FRP. The composite sheets can be molded into various articles usingmethods known in the art including, for example, pressure forming,thermal forming, thermal stamping, vacuum forming, compression forming,and autoclaving. The combination of high stiffness to weight ratio,ability to be thermoformed with deep draw sections, end of liferecyclability, acoustics and desirable low flame spread index, heatrelease, smoke density and gas emission properties make the porousfiber-reinforced thermoplastic composite a more desirable product thanthe products currently being used.

The invention will be further described by reference to the followingexamples which are presented for the purpose of illustration only andare not intended to limit the scope of the invention. Unless otherwiseindicated, all amounts are listed as parts by weight.

Comparative example tests comparing the flame, smoke and gaseousemissions of a control sample designated Sample A and exemplary samplesof an embodiment of the invention designated Samples B and C. Sample Ais a porous fiber-reinforced sheet formed from a blend ofpoly(ether-imide), commercially available from General Electric Companyunder the ULTEM trademark, and bisphenol A polycarbonate resincontaining a bromine based fire retardant additive, commerciallyavailable from General Electric Company under the LEXAN trademark, theresins blended in weight ratios of 5 percent and 55 percent. The blendedresins were dispersed in a porous fiber-reinforced sheet containingabout 40 weight percent glass fibers having a nominal fiber diameter of16 microns and an average length of 12.7 mm. Sample B is the porousfiber-reinforced sheet of Sample A laminated with 76 micron thickpoly(ether-imide) films, commercially available from General ElectricCompany under the ULTEM trademark, in accordance with an embodiment ofthe present invention. Sample C is the porous fiber-reinforced sheet ofSample A laminated with 27 g/m² aramid scrims, commercially availablefrom E.I. du Pont de Nemours and Company under the KEVLAR trademarklaminated onto the exterior surfaces in accordance with an embodiment ofthe present invention. Sample D is the porous fiber-reinforced sheet ofSample A laminated with 8 mil thick polypropylene films. Sample D is acomparative sample that contains laminated polypropylene films that havean LOI of 17. The results are presented below in Tables I to II.

Comparative example tests comparing the flame and smoke characteristicsof Sample E, a porous fiber-reinforced sheet formed from a blend ofpoly(ether-imide) and polycarbonate resins in weight ratio of 25 percenteach with 50 weight percent glass fibers of 16 micron in diameter and12.7 mm in length, Sample F, a porous fiber-reinforced sheet formed froma blend of poly(ether-imide) and an eco-friendly flame retardant basedpolycarbonate resin in a weight ratios of 5 and 55 percent combined with40 weight percent glass fibers of 16 microns diameter and 12.7 mmlength, Sample G, a porous fiber-reinforced sheet formed from apolycarbonate resin with 50 weight percent glass fibers of 16 microndiameter and 12.7 mm length, Sample H, a porous fiber-reinforced sheetformed from polypropylene with 55 weight percent glass fibers of 16micron diameter and 12.7 mm length, Sample I, a porous fiber-reinforcedsheet formed from a polyarylene ether resin with 50 weight percent glassfibers, and Sample J, a porous fiber-reinforced sheet formed from blendof polycarbonate and polybutylene terephthalate combined in a weightratio of 33 percent and 17 percent each with 50 weight percent glassfibers of 16 micron diameter and 12.7 mm length are presented below inTable IV.

The fiber-reinforced thermoplastic sheets for Samples A-J were madeusing the wet-laid paper making process described in United KingdomPatent Nos. 1129757 and 1329409. The fiber-reinforced thermoplasticsheet was further subjected to heat and pressure in a double beltlaminator at 325° C. and 2 bar to partially consolidate the sheet andhave the resin wet the fibers. Sample B was prepared from the samefiber-reinforced thermoplastic sheet as Sample A, but with a 75micrometer thick poly(ether-imide) film covering the surfaces using thedouble belt laminator under the conditions described above. Sample C wasprepared from the same fiber-reinforced thermoplastic sheet as Sample A,but with a 27 g/m² aramid scrim covering the surfaces using the doublebelt laminator under the conditions described above. Sample D wasprepared from the same fiber-reinforced thermoplastic sheet as Sample A,but with a 8 mil thick polypropylene film covering the surfaces usingthe double belt laminator under the conditions described above.

The flame characteristics were measured using a radiant heat source andan inclined specimen of the sample material in accordance with ASTMmethod E-162-02A titled Standard Method for Surface Flammability ofMaterials Using a Radiant Heat Energy Source. A flame spread index wasderived from the rate of progress of the flame front and the rate ofheat liberation by the material under test. Key criteria are a flamespread index (FSI) and dripping/burning dripping observations. UnitedStates and Canadian requirements for passenger bus applications forinterior materials are a FSI of 35 or less with no flaming drips. TheUnderwriters Laboratory (UL) requires that parts greater than 10 squarefeet should have an FSI of 200 or less to obtain a listing from UL.

The smoke characteristics were measured by exposing test specimens toflaming and non flaming conditions within a closed chamber according toASTM method E-662-03 titled Standard Test Method for Specific OpticalDensity of Smoke Generated by Solid Materials. Light transmissionsmeasurements were made and used to calculate specific optical density ofthe smoke generated during the test time period. Key criteria are anoptical density (D_(s)) of smoke produced by a sample exposed to aradiant furnace or a radiant furnace plus multiple flames. The opticaldensity is plotted versus time for generally 20 minutes. Maximum opticaldensity and time to reach this maximum are important outputs. UnitedStates and Canadian Rail regulations and some United States and CanadianBus guidelines set a maximum D_(s) of 100 or less at 1.5 minutes, and amaximum D_(s) of 200 or less at 4 minutes. Global Air regulations setsthe D_(s) at 4 minutes for many large interior applications at 200 orless.

FAA requirements for toxicity and flame were also measured in accordanceFAA tests BSS-7239, developed by Boeing Corporation., and FAR 25.853 (a)Appendix F, Part IV (OSU 65/65) Calorimeter.

A large part in an aircraft passenger cabin interior typically will needto meet the ASTM E162 and ASTM E662 described above as well a maximumD_(s) of 200 at 4 minutes. A difficult test for plastics hastraditionally been the OSU 65/65 heat release test. In this test, thetest material is exposed to defined radiant heat source, and calorimetermeasurements are recorded. Key criteria are an average maximum heatrelease during the 5 minute test that should not exceed 65 kW/m², and anaverage total heat released during the first 2 minutes of the test thatshould not exceed 65 kW-min/m².

In the 60 second vertical burn test, the part is exposed to asmall-scale open flame for 60 seconds and the key criteria are a burnedlength of 150 mm or less, an after flame time of 15 seconds or less, andflame time drippings of 3 seconds or less.

TABLE I Test Method Sample A Sample B Sample C Sample D ASTM E-162:Average Flame Spread Index F_(s) 10 5.5 6.0 >200 Flaming Drips None NoneNone Yes ASTM E-662: Smoke Density D_(s) at 1.5 minutes 9 2 6 6 SmokeDensity D_(s) at 4.0 minutes 65 25 133 133 Maximum Smoke DensityD_(sMax) 315 182 289 289 FAR 25.853 (a) Appendix F, Part IV: N/A 2minutes Total Heat Release 54 kW/m² 45 kW/m² 48 kW/m² Maximum HeatRelease 54 KW/m² 41 KW/m² 48 KW/m² 60 Second Vertical Burn: VerticalBurn Time Pass Pass Pass Burn Length 91.4 mm 61.0 mm 53.3 mm

TABLE II BSS-7239: Sample A Sample B Gases (ppm at 4 minutes) (ppm at 4minutes) HCN 1 1 CO 200 100 NO + NO₃ 2 2 SO₂ <1 <1 HF <1 <1 HCL 2 1

TABLE III Sample Sample Sample Sample Sample Sample Test Method E F G HI J ASTM E-162: F_(s) 27.5 50 45 245 39 69 Flaming Drips None None NoneF.D.* None None ASTM E-662: N/A D_(s) at 1.5 13 18 21 28 16 minutesD_(s) at 4.0 114 100 146 53 79 minutes Max. D_(sMax) 299 388 495 59 294*F.D. = flaming drips.

The above test results show that the fiber reinforced thermoplasticsheet with poly(ether imide) skins of Sample B and with aramid scrims ofSample C exhibit a reduced flame spread index F_(s), a reduced smokedensity D_(s), reduced heat release, and reduced gaseous emissions overSample A. As shown in Table 1, Samples B and C exhibit test results thatare superior to the test results of Sample A. For example, Samples B andC exhibited a lower flame spread index F_(s), 5.5 and 6.0 respectively,than Sample A, which had a F_(s) of 10. Particularly, Samples B and Cexhibited lower test results for the tests run according to ASTM E-162,ASTM E-662, FAR 25.853(a), and the 60 second vertical burn test. Theonly anomaly being the 4 minute smoke density D_(s) result of Sample C.Comparative Example D, which included a thermoplastic film having an LOIof only 17, exhibited a flame spread index F_(s) of greater than 200 andexhibited flaming drips. Further, each of samples E-J exhibit at leastone of a flame spread index F_(s) and a four minute smoke density D_(s)that are significantly higher than the flame spread index F_(s) and thefour minute smoke density D_(s) of Samples B and C.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

1. A composite sheet material comprising: at least one porous core layercomprising at least one thermoplastic material and from about 20 weightpercent to about 80 weight percent reinforcing fibers based on a totalweight of said porous core layer, said porous core layer having a voidcontent of about 5 percent to about 95 percent; and at least one skin,each said skin covering at least a portion of a surface of said at leastone porous core layer, said skin comprising at least one of athermoplastic film, an elastomeric film, a thermosetting coating, aninorganic coating, a fiber based scrim, a non-woven fabric, and a wovenfabric, said skin having a limiting oxygen index greater than about 22,as measured per ISO
 4589. 2. A composite sheet material in accordancewith claim 1 wherein said thermoplastic film comprises at least one ofpoly(ether imide), poly(ether ketone), poly(ether-ether ketone),poly(phenylene sulfide), poly(arylene sulfone), poly(ether sulfone),poly(amide-imide), poly(1,4-phenylene), polycarbonate, nylon, andsilicone.
 3. A composite sheet material in accordance with claim 1wherein said fiber based scrim comprises at least one of glass fibers,aramid fibers, graphite fibers, carbon fibers, inorganic mineral fibers,metal fibers, metalized synthetic fibers, and metalized inorganicfibers.
 4. A composite sheet material in accordance with claim 3 whereinsaid fiber based scrim comprises at least one of polyacrylonitrile,p-aramid, m-aramid, poly(p-phenylene 2,6, benzobisoxazole),poly(ether-imide) and poly(phenylene sulfide).
 5. A composite materialin accordance with claim 1 wherein said thermosetting coating comprisesat least one of unsaturated polyurethanes, vinyl esters, phenolics andepoxies.
 6. A composite material in accordance with claim 1 wherein saidinorganic coating comprises minerals containing cations selected fromCa, Mg, Ba, Si, Zn, Ti and Al.
 7. A composite material in accordancewith claim 6 wherein said inorganic coating comprises at least one ofgypsum, calcium carbonate and mortar.
 8. A composite sheet material inaccordance with claim 1 comprising: a first porous core layer having afirst surface and a second surface; and at least one skin covering atleast a portion of at least one of said first and second surface.
 9. Acomposite sheet material in accordance with claim 1 comprising: a firstand a second porous core layer, each said core layer comprising a firstand a second surface, said second surface of said first core layerpositioned adjacent said first surface of said second core layer; and atleast one skin covering at least a portion of at least one of said firstand second surfaces of said first core layer and said first and secondsurface of said second core layer.
 10. A composite sheet material inaccordance with claim 9 wherein said first porous core layer comprisesat least one of a different thermoplastic material and a different fiberthan said second porous core layer.
 11. A composite sheet material inaccordance with claim 1 comprising: a first, a second, and a thirdporous core layer, each said core layer comprising a first and a secondsurface, said second surface of said first core layer positionedadjacent said first surface of said second core layer, said secondsurface of said second core layer positioned adjacent said first surfaceof said third core layer; and at least one skin covering at least one ofsaid first and second surfaces of said first core layer, said first andsecond surface of said second core layer, and said first and secondsurface of said third core layer.
 12. A composite sheet material inaccordance with claim 11 wherein one of said porous core layerscomprises at least one of a different thermoplastic material and adifferent fiber than at least one of said other layers.
 13. A method ofmanufacturing a porous fiber-reinforced thermoplastic sheet, said methodcomprising: providing a porous fiber-reinforced thermoplastic sheetcomprising at least one porous core layer comprising a thermoplasticmaterial and from about 20 weight percent to about 80 weight percentreinforcing fibers, each porous core layer having a void content ofabout 5 percent to about 95 percent; and laminating at least one skin toa surface of the porous fiber-reinforced thermoplastic sheet, each skincomprising at least one of a thermoplastic film, an elastomeric film, athermosetting coating, an inorganic coating, a fiber based scrim, anon-woven fabric, and a woven fabric, the skin having a limiting oxygenindex greater than about 22, as measured per ISO 4589 to enhance atleast one of the flame, smoke, heat release and gaseous emissionscharacteristics of the porous fiber-reinforced thermoplastic sheet. 14.A method in accordance with claim 13 wherein the thermoplastic filmcomprises at least one of poly(ether imide), poly(ether ketone),poly(ether-ether ketone), poly(phenylene sulfide), poly(arylenesulfone), poly(ether sulfone), poly(amide-imide), poly(1,4-phenylene),polycarbonate, nylon, and silicone.
 15. A method in accordance withclaim 13 wherein the fiber based scrim comprises at least one of glassfibers, aramid fibers, graphite fibers, carbon fibers, inorganic mineralfibers, metal fibers, metalized synthetic fibers, and metalizedinorganic fibers.
 16. A method in accordance with claim 15 wherein thefiber based scrim comprises at least one of polyacrylonitrile, p-aramid,m-aramid, poly(p-phenylene 2,6, benzobisoxazole), poly(ether-imide) andpoly(phenylene sulfide).
 17. A method in accordance with claim 13wherein the thermosetting coating comprises at least one of unsaturatedpolyurethanes, vinyl esters, phenolics and epoxies.
 18. A method inaccordance with claim 13 wherein the inorganic coating comprisesminerals containing cations selected from Ca, Mg, Ba, Si, Zn, Ti and Al.19. A method in accordance with claim 18 wherein the inorganic coatingcomprises at least one of gypsum, calcium carbonate and mortar.
 20. Amethod in accordance with claim 13 wherein said providing a porous fiberreinforced thermoplastic sheet comprises providing a porous fiberreinforced thermoplastic sheet comprising a first porous core layerhaving a first surface and a second surface, and said laminating atleast one skin comprises laminating at least one skin covering at leastone of said first and second surface.
 21. A method in accordance withclaim 13 wherein said providing a porous fiber reinforced thermoplasticsheet comprises providing a porous fiber reinforced thermoplastic sheetcomprising a first and a second porous core layer, each core layercomprising a first and a second surface, the second surface of the firstcore layer positioned adjacent the first surface of the second corelayer, and said laminating at least one skin comprises laminating atleast one skin covering at least one of the first and second surfaces ofthe first core layer and the first and second surface of the second corelayer.
 22. A method in accordance with claim 13 wherein said providing aporous fiber reinforced thermoplastic sheet comprises providing a porousfiber reinforced thermoplastic sheet comprising a first, a second, and athird porous core layer, each core layer comprising a first and a secondsurface, the second surface of the first core layer positioned adjacentthe first surface of the second core layer, the second surface of thesecond core layer positioned adjacent the first surface of the thirdcore layer, and said laminating at least one skin comprises laminatingat least one skin covering at least one of the first and second surfacesof the first core layer, the first and second surface of the second corelayer, and the first and second surface of the third core layer.
 23. Amethod in accordance with claim 13 wherein the skin comprises at leastone of a fiber based scrim, a non-woven fabric and a woven fabric.
 24. Acomposite sheet material comprising: a permeable core comprisingdiscontinuous reinforcing fibers bonded together with a thermoplasticresin, said permeable core having a density from about 0.2 gm/cc toabout 1.8 gm/cc, and a void content of about 5 percent to about 95percent, said permeable core including a surface region; and an adherentlayer adjacent to said surface region, said adherent layer comprising amaterial having a limiting oxygen index greater than about 22, asmeasured per ISO
 4589. 25. A composite sheet material according to claim24 wherein said permeable core has an open cell structure.
 26. Acomposite sheet material according to claim 24 wherein said permeablecore comprises at least one of metal fibers, metalized inorganic fibers,metalized synthetic fibers, glass fibers, graphite fibers, carbonfibers, ceramic fibers, and aramid fibers.
 27. A composite sheetmaterial according to claim 24 wherein said permeable core comprises athermoplastic resin selected from the group consisting of polyethylene,polypropylene, polystyrene, acrylonitrylstyrene, butadiene,polyethyleneterephthalate, polybutyleneterephthalate,polybutyleneterachlorate, polyvinyl chloride, polyphenylene ether,polycarbonates, polyestercarbonates, thermoplastic polyesters,polyetherimides, acrylonitrile-butylacrylate-styrene polymers, amorphousnylon, polyarylene ether ketone, polyphenylene sulfide, polyarylsulfone, polyether sulfone, poly(1,4 phenylene) compounds, silicones andmixtures thereof.
 28. A composite sheet material according to claim 24wherein said core comprises from about 20 to about 80 percent by weightfibers and from about 20 to about 80 percent by weight of athermoplastic resin.
 29. A composite sheet material according to claim24 wherein said core comprises from about 35 to about 55 percent byweight fibers and from about 45 to about 65 percent by weight of athermoplastic resin.
 30. A composite sheet material according to claim24 wherein said composite has a four minute smoke density, Ds, of lessthan about 200 when tested in accordance with ASTM E662.
 31. A compositesheet material according to claim 26 having a thickness from about 0.5mm to about 25 mm.
 32. A composite sheet material according to claim 26wherein said adherent layer has a thickness from about 25 micrometers toabout 2.5 mm.
 33. A composite sheet material according to claim 26wherein said adherent adjacent layer comprises at least one of athermoplastic film, an elastomeric film, a thermosetting coating, aninorganic coating, a fiber based scrim, a non-woven fabric, and a wovenfabric, said skin having a limiting oxygen index greater than about 22,as measured per ISO
 4589. 34. A composite sheet material in accordancewith claim 33 wherein said thermoplastic film comprises at least one ofpoly(ether imide), poly(ether ketone), poly(ether-ether ketone),poly(phenylene sulfide), poly(arylene sulfone), poly(ether sulfone),poly(amide-imide), poly(1,4-phenylene), polycarbonate, nylon, andsilicone.
 35. A composite sheet material in accordance with claim 33wherein said fiber based scrim comprises at least one of glass fibers,aramid fibers, graphite fibers, carbon fibers, inorganic mineral fibers,metal fibers, metalized synthetic fibers, and metalized inorganicfibers.
 36. A composite sheet material in accordance with claim 33wherein said fiber based scrim comprises at least one ofpolyacrylonitrile, p-aramid, m-aramid, poly(p-phenylene 2,6,benzobisoxazole), poly(ether-imide) and poly(phenylene sulfide).
 37. Acomposite material in accordance with claim 33 wherein saidthermosetting coating comprises at least one of unsaturatedpolyurethanes, vinyl esters, phenolics and epoxies.
 38. A compositematerial in accordance with claim 33 wherein said inorganic coatingcomprises of minerals containing cations selected from Ca, Mg, Ba, Si,Zn, Ti and Al.
 39. A composite material in accordance with claim 38wherein said inorganic coating comprises at least one of gypsum, calciumcarbonate and mortar.
 40. A composite sheet material in accordance withclaim 1 wherein said at least one porous core layer is formed by aprocess selected from the group consisting essentially of a wet laidprocess, an air laid process, a dry blend process, and a carding andneedle process.
 41. A method in accordance with claim 13 wherein theporous fiber-reinforcing thermoplastic sheet is formed by a processselected from the group consisting essentially of a wet laid process, anair laid process, a dry blend process, and a carding and needle process.42. A composite sheet material in accordance with claim 24 wherein saidpermeable core is formed by a process selected from the group consistingessentially of a wet laid process, an air laid process, a dry blendprocess, and a carding and needle process.